Electric Motor with Fluid Cooling

ABSTRACT

The present disclosure relates to electric motors having fluid cooling by fluid flow through a cooling jacket cavity. An electric motor may include a cylindrical housing wall, a stator mounted to an inner surface of the housing wall, a motor shaft mounted for rotation within the housing wall, and a cooling jacket wall concentric with and at least partially surrounding the housing wall. A housing wall outer surface and a jacket wall inner surface define a cooling jacket cavity through which cooling fluid flows to draw heat way from the electric motor. Heat slingers, axial or radial fans or the like mounted on one or two ends of the motor shaft extending from the housing wall may further assist in dissipating heat generated by the electric motor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Ser. No. 16/726,711, filed on Dec. 24, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62/750,053, filed on Oct. 24, 2018, which applications are expressly incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to industrial electric motors and, more particularly, to industrial electric motors for high temperature environments that are cooled by fluid flow over an electric motor housing and reduce thermal heat transfer through conduction and convection.

BACKGROUND

Electric motors are used in industrial applications to create airflow for processes such as combustion, ventilation, aeration, particulate transport, exhaust, cooling, air-cleaning, drying and air recirculation. Airflow is created by rotating an impeller having a plurality of blades to create the desired circulation of air within the operating environment. Typically, an industrial electric motor includes an external motor housing, internal components within the housing such as a stator and a rotor, and a motor shaft extending out of the motor housing. The impeller is mounted on or otherwise operatively connected to the motor shaft so that rotation of the motor shaft causes rotation of the impeller to generate the airflow. In many high temperature environment applications, the motor housing is mounted to an exterior wall or roof of the high temperature environment with the motor shaft extending through the wall or roof and the impeller being disposed within the high temperature environment.

The components of the industrial electric motors are subjected to loads and stresses during the operation in high temperature environments. Thermal stresses along with the normal loads and stresses of operating electric motors can cause damage to the components that will reduce the efficiency of the electric motor or cause complete failure. The high temperature environments can also subject the components to contaminants that may corrode the components or otherwise damage the components so that the electric motors do not operate at their optimal efficiencies. Ultimately, the additional thermal stresses and other adverse conditions can result in earlier fatigue failure of the industrial electric motor and more frequent need for replacement of components in high temperature environments as the components endure numerous thermal cycles from processes, and in corrosive environments due to exposure to harmful chemicals, than when operating in environments that do not cause the same level of thermal stresses or corrosive exposure on the components. Moreover, when operating on a variable drive frequency (VFD) controller, an electric motor may have an excessive turndown ratio that can cause the internal components of the motor to run much hotter at lower frequency, thus causing an overheating condition where the motor is not be able to dissipate the additional heat through the motor housing through traditional convective or conductive cooling methods.

The high temperature environments may require high motor speeds to generate the air flow volumes and capacities required for regulating the temperatures of the environments. The faster the rotor and the impeller are required to rotate under heat, the weaker the materials in the rotating components become as the molecules expand, thereby reducing the strength of the components. In particular, the shaft of the motor may be affected by the heat and rotation. As centrifugal forces are applied to the spinning mass, shaft strength is essential under heat. Moreover, many high temperature applications require the shaft to extend through insulation-lined furnace or oven walls so the ambient surroundings remain cool while the process heat is high inside of the furnace or oven, which can increase shear loads and bending moments on the shaft.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, an electric motor is disclosed. The electric motor may include a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface, a housing wall outer surface, a first motor housing end and a second motor housing end, a stator mounted to the housing wall inner surface, and a motor shaft mounted for rotation within the housing wall and having a first shaft end extending out of the first motor housing end, a second shaft end extending out of the second motor housing end and a shaft longitudinal axis. The electric motor may further include a rotor mounted on the motor shaft and aligned with the stator, a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity, a first heat slinger mounted on the first shaft end, and a second heat slinger mounted on the second shaft end and disposed within the cooling jacket.

In another aspect of the present disclosure, an electric motor is disclosed. The electric motor may include a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface and a housing wall outer surface, a stator mounted to the housing wall inner surface and a motor shaft mounted for rotation within the housing wall and having a shaft longitudinal axis. The electric motor may further include a rotor mounted on the motor shaft and aligned with the stator, a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity, and a cooling fan mounted at an open end of the jacket wall and upstream from the housing wall to discharge air into the cooling jacket cavity, wherein the air discharged from the cooling fan flows longitudinally through the cooling jacket cavity and along the housing wall outer surface.

In a further aspect of the present disclosure, an electric motor mounted on a base plate of a fan mount assembly is disclosed. The electric motor may include a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface, a housing wall outer surface and a motor housing base bracket extending from the housing wall outer surface and affixed to the base plate, a stator mounted to the housing wall inner surface, and a motor shaft mounted for rotation within the housing wall and having a shaft longitudinal axis and a first shaft end extending from a first motor housing end of the motor housing. The electric motor may further include a rotor mounted on the motor shaft and aligned with the stator, a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity, and an external bearing external to the first motor housing end and mounted on the base plate, wherein the external bearing receives and supports the first shaft end.

Additional aspects are defined by the claims of this patent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an electric motor including an embodiment of fluid cooling in accordance with the present disclosure;

FIG. 2 is a second isometric view of the electric motor of FIG. 1;

FIG. 3 is a third isometric view of the electric motor of FIG. 1;

FIG. 4 is a cross-sectional view of the electric motor of FIG. 1 taken through line 4-4 of FIG. 2;

FIG. 5A is a cross-sectional view of the electric motor of FIG. 1 taken through line 5A-5A of FIG. 4;

FIG. 5B is a cross-sectional view of the electric motor of FIG. 1 taken through line 5B-5B of FIG. 4;

FIG. 5C is a cross-sectional view of the electric motor of FIG. 1 taken through line 5C-5C of FIG. 4;

FIG. 6 is an isometric view of an electric motor including a second embodiment of fluid cooling in accordance with the present disclosure;

FIG. 7 is a second isometric view of the electric motor of FIG. 6;

FIG. 8 is a third isometric view of the electric motor of FIG. 6;

FIG. 9 is a cross-sectional view of the electric motor of FIG. 6 taken through line 9-9 of FIG. 7;

FIG. 10 is a cross-sectional view of the electric motor of FIG. 6 taken through line 10-10 of FIG. 9;

FIG. 11 is an isometric view of an electric motor including a further alternative embodiment of fluid cooling in accordance with the present disclosure;

FIG. 12 is a second isometric view of the electric motor of FIG. 11;

FIG. 13 is the isometric view of the electric motor of FIG. 11 with a cooling jacket and a fan housing removed;

FIG. 14 is a side view of the electric motor of FIG. 11 with the cooling jacket and the fan housing removed;

FIG. 15 is a cross-sectional view of the electric motor of FIG. 11 taken through line 15-15 of FIG. 13; and

FIG. 16 is an isometric view of the electric motor of FIG. 11 with a second slinger replaced by an axial impeller.

DETAILED DESCRIPTION

The present disclosure is directed to electric motors having housings and other features for causing fluid flow around the electric components to remove heat during operation. The electric motors in accordance with the present disclosure have particular application in high temperature environments where the electric motors drive impellers to create airflow within the high temperature environments. The housing of the electric motor may be mounted to an exterior surface such as a wall or roof of the high temperature environment with a shaft extending into the high temperature and/or corrosive environment where the impeller will be located. Heat may still be communicated from the high temperature to the electric motor housing where the cooling jackets and other components in accordance with the present disclosure remove heat to protect the internal components of the electric motor, as well as other critical components, such as bearing, O-rings and radial lip seals and the like, that may be included in the construction of the specialty motor.

FIGS. 1-3 illustrate isometric views of a first embodiment of an electric motor 10 with fluid cooling in accordance with the present disclosure. The electric motor 10 may be a standard 3 phase A/C induction motor and may include a motor housing 12 enclosing the electrical components discussed later in the present application. The motor housing 12 includes a housing wall 14 with a first or mounting flange 16 at a first end and a second or closed end flange 18 at an opposite end. The flanges 16, 18 may be integrally formed at the corresponding ends of the housing wall 14, or welded or otherwise connected to the ends to from substantially air- and water-tight connections so gases and fluids cannot leak into or out of the motor housing 12 at the interfaces between the housing wall 14 and the flanges 16, 18. The mounting flange 16 is annular and configured for connection to a wall or roof (not shown) of a high temperature environment with a shaft end 20 of a motor shaft 22 extending through the mounting flange 16 and into the high temperature environment for attachment of an impeller (not shown) that will be driven by the electric motor 10 to create airflow within the high temperature environment. It should be noted that electric motors in accordance with the present disclosure can also be used to create airflow in other controlled atmosphere environments, such as gas-tight/vacuum environments or oxygen free environments that may be required for processes or materials to avoid oxidation or contamination of the processes or materials within the environment. The second flange 18 is configured for attachment of an end bell 24 and an end cap 26 to close off the motor housing as discussed more fully below. The motor housing 12 may further include a wire terminal box 28 for the electrical connections between the motor components and a power source and controls (not shown) for the electric motor 10, and a thermostat box 30 for a thermostat (not shown) that may measure the internal temperature of the motor housing 12 to provide feedback for detecting overheating conditions that may happen in the case of power outages for the cooling liquid supply, water flow shortages or other cooling medium disruptions.

Cooling of the motor housing 12 is provided by a cooling jacket 32 that surrounds the housing wall 14 to facilitate fluid flow over the housing wall 14 to remove heat from the motor housing 12. The interior of the cooling jacket 32 includes a cylindrical jacket wall 34 surrounding and concentrically aligned with the housing wall 14. The jacket wall 34 may be integrally formed with, or welded or otherwise connected to the mounting flange 16 to form an air- and water-tight seal there between. At an end opposite the mounting flange 16, an annular jacket end wall 36 extends from the end of the jacket wall 34 to the housing wall 14 and is connected thereto to close off the end of the cooling jacket 32. In the illustrated embodiment, the jacket wall 34 includes a cutout portion 38 extending from the mounting flange 16 and providing access to a corresponding portion of the housing wall 14. The cooling jacket 32 is closed in the area of the cutout portion 38 by a pair of cutout side walls 40 and a cutout end wall 42. The cutout portion 38 may provide access for installation of a grease fitting 44 proximate the mounting flange 16 to provide lubrication to a fixed shaft bearing 46 (FIG. 2) without the necessity of opening the motor housing 12 or detaching the electric motor 10 to gain access to the fixed shaft bearing 46 through a central circular opening 48 of the mounting flange 16. The mounting flange 16 may include an annular seal groove machined into the central circular opening 48 to receive an O-ring or other seal to form a gas-tight connection between the mounting flange 16 and a surface of a wall of the environment to which the electric motor 10 is mounted.

Access for the cooling fluid to the cooling jacket 32 is provided by a fluid inlet port 50 (FIG. 3) and a fluid outlet port 52 (FIGS. 1 and 2) in the jacket wall 34. The fluid inlet port 50 is located proximate the mounting flange 16 in an area that is most proximate to the heat from the high temperature environment. The fluid inlet port 50 is also proximate a lowest portion of the motor housing 12 when the electric motor 10 is mounted with the motor shaft 22 horizontal and the wire terminal box 28 on top of the motor housing 12. Being positioned proximate the mounting flange 16, the fluid inlet port 50 is also proximate the lowest point of the motor housing 12 when the electric motor 10 is oriented with the end 20 of the motor shaft 22 extending vertically downward, such as when the electric motor 10 is installed on a roof of a high temperature environment or other controlled atmosphere environment.

The fluid outlet port 52 is located proximate the jacket end wall 36 and on the same side of the motor housing 12 as the wire terminal box 28. Positioned as shown, the fluid outlet port 52 is disposed proximate the top of the motor housing 12 and the cooling jacket 32, and above the fluid inlet port 50 whether the electric motor 10 is oriented horizontally with the wire terminal box on top or vertically with the motor shaft 22 extending downward. With this arrangement, air pockets within the cooling jacket 32 that can reduce the thermal efficiency of the cooling jacket 32 may be virtually eliminated as discussed further below.

To facilitate orienting the electric motor 10 horizontally or vertically as discussed above for installation, a plurality of lifting gussets 60 are circumferentially spaced about the cooling jacket 32 proximate the mounting flange 16. The lifting gussets 60 may be welded to the outer surface of the jacket wall 34 and to the mounting flange 16, thereby providing structural reinforcement for the mounting flange 16 in addition to being points of attachment for lifting elements. The lifting gussets 60 may each include a connection aperture 62 for attachment of hooks, chain, cables, ropes or other lifting elements. An additional lifting gusset 64 with a connection aperture 66 may be welded to the housing wall 14 within the cutout portion 38 of the jacket wall 34.

The interior of the electric motor 10 is illustrated in detail in the cross-sectional view of FIG. 4. The electrical components of the electric motor 10 are installed within the housing wall 14. A stator 70 is mounted to a housing wall inner surface 72 and is held stationary relative to the housing wall 14. A rotor 74 is mounted on and rotates with the motor shaft 22 about a shaft longitudinal axis 76. The operation of the stator 70 and the rotor 74 to drive the motor shaft 22 and attached impeller is conventional for a 3 phase A/C induction motor as is known to those skilled in the art.

The motor shaft 22 has different operating requirements within the motor housing 12 and within the high temperature environment. Within the motor housing 12, the motor shaft 22 must be electrically conductive so as to not interfere with the magnetic field and current flow of the stator 70 and the rotor 74. Outside the motor housing 12 and proximate to and within the high temperature environment, the motor shaft 22 must be resistant to high temperatures. To accommodate both sets of operating conditions, the motor shaft 22 may be provided with a two-piece construction. A motor housing shaft portion 78 within the motor housing 12 may be fabricated from a conductive material such as 1018 or 1045 carbon steel or similar conductive material. An exterior shaft portion 80 external to the motor housing 12 may be fabricated from a non-conductive, high temperature resistant material such as 300 series stainless steel alloys (approximate melting point=2750° F.), nickel steel alloys (approximate melting point=2647° F.), chromium steel (approximate melting point=3380° F.) or similar materials having melting points of approximately 2200° F. or higher. These materials aid in reduction of heat transfer through the motor shaft 22 to critical components such as bearings and seals that take or operate in extreme heat without risking damage. Due to the centrifugal forces applied from the impeller rotating on the motor shaft 22, the material of the exterior shaft portion 80 may require a very high tensile strength, a high modulus of elasticity and high resistance to creep at the elevated temperatures where standard carbon or mild steel elements would not be up to the challenge. Resistance to shaft deflection is taken into consideration in material selection to ensure a long service life for the motor shaft 22. The shaft portions 78, 80 may be fabricated separately and assembled prior to installation. In one embodiment, the motor housing shaft portion 78 may have a splined male end 82 that is inserted into a splined bore 84 of the exterior shaft portion 80, with the splines of the male end 82 and the bore 84 meshing and engaging so that the shaft portions 78, 80 rotate together. Due to the operation in extreme heat conditions, one or both shaft portions 78, 80 may include heat dissipation bores 86 drilled through the shaft portions 78, 80 transverse to the longitudinal axis 76. The heat dissipation bores 86 increase the exposed surface area of the motor shaft 22 that allow heat to be communicated to the atmosphere surround the motor shaft 22.

The motor shaft 22 is mounted to the motor housing 12 for rotation using appropriate rotational bearings. The fixed shaft bearing 46 discussed above is disposed proximate the mounting flange 16, and is accessible through the circular opening 48 of the mounting flange 16 when the electric motor 10 is not installed. In one embodiment, the fixed shaft bearing 46 may be a pillow block bearing. Bearings such as pillow block bearings may allow rotation of the motor shaft 22 while forming a seal to prevent unwanted contaminants from entering the motor housing 12 from the high temperature environment. An annular bearing mounting flange 92 may be connected to and extend inward from the housing wall inner surface 72. The fixed shaft bearing 46 may have an outer housing that is press fit into, welded to or otherwise connected to the bearing mounting flange 92 to center the fixed shaft bearing 46 within the motor housing 12.

At the opposite end of the motor housing 12 proximate the closed end flange 18, a floating shaft bearing 94 may be mounted within the end bell 24 of the motor housing 12. The floating shaft bearing 94 may be any appropriate ball bearing for the motor shaft 22. Even with the cooling jacket 32 removing heat from the motor housing 12, the motor shaft 22 may still deflect due to natural flexing motion caused by rotational and centrifugal forces applied due to the inertia of the impeller. The motor shaft 22 may also experience some thermal expansion and contraction due to heat transferred from the high temperature environment, as well as heat generated from rotational loading and power transmission friction from the electric current flowing through the rotor 74 mounted on the motor shaft 22. Pre-loaded bearings or an improperly designed shaft may succumb to heavy vibrations, critical speeds or shaft vibrations. Resistance or non-allowance of shaft expansion could cause heat from the internal balls of the ball bearing not riding smoothly within the raceway of the bearing.

To allow for thermal expansion and contraction of the motor shaft 22, the floating shaft bearing 94 is engaged by the end bell 24 in a manner that allows axial movement of the floating shaft bearing 94 as the motor shaft 22 expands and contracts. In the illustrated embodiment, for example, the floating shaft bearing 94 may have a axial expansion slot 96 defined in an outer surface, such as an outer surface of an outer race. The end bell 24 may have a corresponding threaded expansion set screw bore 98 drilled through from an outer surface to an inner surface. The expansion set screw bore 98 receives an expansion set screw 100 therein. The expansion slot 96 may have a circumferential width wide enough to receive an end of the expansion set screw 100. During installation, the expansion slot 96 may be aligned with the expansion set screw bore 98, and the expansion set screw 100 may be screwed into the expansion set screw bore 98 with the tip being received within the expansion slot 96, but not tightened to the point of preventing axial movement of the floating shaft bearing 94. The expansion slot 96 may have an axial length and an axial position that allows the floating shaft bearing 94 to move axially with the expansion and contraction of the motor shaft 22 without the expansion set screw 100 engaging the longitudinal ends of the expansion slot 96 and restricting movement. At the same time, the expansion set screw 100 will engage lateral sides of the expansion slot 96 to substantially rotation of the floating shaft bearing 94 about the longitudinal axis 76. Alternative mechanisms for allowing axial movement of the floating shaft bearing 94 while preventing rotation will be apparent to those skilled in the art and are contemplated by the inventor. This arrangement can prolong the life of the floating shaft bearing 94 as the motor shaft grows linearly from deflection rather than binding the bearings in the races of the ball bearings and causing thrust loads, additional friction, misalignment and overheating of the floating shaft bearing 94 in a preloaded condition as the motor shaft 22 expands.

Skidding occurs when an applied bearing load is inadequate for developing enough elastohydrodynamic tractive force between the raceway and the rolling elements to overcome cage drag, churning losses and prevention of gyroscopic spin. To prevent skidding or other bearing phenomenon, the inner diameter of the floating shaft bearing 94 and the outer diameter of the corresponding end of the motor shaft 22 may be reduced to reduce load on the floating shaft bearing 94 and allow for proper loading and expansion. Because the highest radial loads may occur at the fixed shaft bearing 46 that is closer to the impeller or rotating rotor affixed to the end 20 of the motor shaft 22, the diameter reduction at the floating shaft bearing 94 may allow for a lower, more ideal load range than would be needed for the higher radial loads at the fixed shaft bearing 46 at the opposite end of the electric motor 10.

Grease or other coating materials, if introduced within the motor housing 12, may adhere to or coat the stator 70 and/or the rotor 74. By coating the electric components 70, 74, the grease or coating material may act as a thermal insulator that seals in heat and create a risk of causing the electric motor 10 to overheat. Consequently, because the floating shaft bearing 94 has potential to leak grease or coating material, a radial restriction bushing and/or lip seal 104 may be installed between the floating shaft bearing 94 and the components 70, 74. In the illustrated embodiment, the lip seal 104 is press fit into the base of the end bell 24 in which the floating shaft bearing 94 is installed. However, the lip seal 104 may be installed at any other location where it can prevent fluids from the floating shaft bearing 94 from leaking into the motor housing 12.

Installation of the end cap 26 substantially seals the interior of the motor housing 12 from the ambient atmosphere surrounding the electric motor 10. The end cap 26 may include a grease fitting 106 similar to the grease fitting 44 proximate the mounting flange 16 for providing lubricant to the floating shaft bearing 94 without removing the end cap 26. The grease fittings 44, 106 contain dust caps that prevent gas from entering or escaping the motor housing 12. The dust caps are in place during normal operation. At service or lubrication, the dust caps are unscrewed and removed, making a standard grease gun accessible to add the appropriate lubricant. After servicing, the dust caps are reinstalled to reseal the motor housing 12. In addition to welds between mating parts, the motor housing 12 will include other sealing mechanisms as necessary at locations to seal the motor housing 12 from the ambient atmosphere. However, in some implementations, contaminants from the high temperature environment may flow past the fixed shaft bearing 46 and into the interior of the motor housing 12. The contaminants can include gases such as ammonia that are corrosive to the materials of the stator 70 and the rotor 74 and do damage that may impact the performance of the electric motor 10. The grease or other coating materials on the stator 70, the rotor 74 and other copper parts may help to protect these internal motor components from such contaminants within the motor housing 12. To further protect the internal components, the end bell 24 may include an inert gas purge port 108 (FIG. 3) that is in fluid communication with the interior of the motor housing 12. The inert gas purge port 108 may be connected to a source (not shown) of pressurized inert gas that will not react with and corrode the stator 70 and the rotor 74. The inert gas can be pumped into the interior of the motor housing 12 to raise the internal pressure to a point that is greater than the pressure at the outer side of the fixed shaft bearing 46. The internal pressure created by the inert gas will keep the unwanted contaminants from infiltrating the interior of the motor housing 12. When inert gas purging is not needed, the inter gas purge port 108 may be plugged to hermetically seal the interior of the motor housing 12 from the ambient atmosphere.

The interior of the cooling jacket 32 is also shown in FIG. 4. A housing wall outer surface 110, a jacket wall inner surface 112, the mounting flange 16, the jacket end wall 36 and the cutout end wall 42 define a cooling jacket cavity 114 through which the cooling fluid will flow from the fluid inlet port 50 to the fluid outlet port 52. As shown, the cooling jacket cavity 114 extends from the mounting flange 16 to a point where substantially all of the stator 70 and the rotor 74 are encircled by the cooling jacket 32. In alternative embodiments, the cooling jacket 32 may extend further or shorter to meet the heat transfer requirements for a particular implementation of the electric motor 10. The cooling fluid may be any fluid having heat transfer properties sufficient to remove the required heat from the motor housing 12. Where no source of liquid coolant is available, pressurized air may function as the coolant fluid to create airflow over the housing wall outer surface 110. In most applications, pressurized water functions as the coolant fluid and is pumped through the cooling jacket cavity 114. In alternative embodiments, other liquid coolants such as polyalkylene glycol (PAG), cutting fluid, oils, other waterless coolants and the like may be used to achieve a desired level of heat transfer.

Due to the positioning of the fluid inlet port 50 at the bottom and the fluid outlet port 52 at the top of the cooling jacket 32 as described above, the coolant such as water will flow through and substantially fill the entire cooling jacket cavity 114 with minimal air gaps forming. In some implementations, it may be desirable to promote coolant fluid flow through a particular path within the cooling jacket cavity 114 that increases fluid flow over the housing wall outer surface 110. In the illustrated embodiment, the coolant flow through the cooling jacket cavity 114 is facilitated by a first flow control ring 120 and a second flow control ring 122. In this embodiment, the cutout end wall 42 may be a portion of the second flow control ring 122 at the cutout portion 38 of the jacket wall 34. In alternative embodiment, the cutout end wall 42 and the second flow control ring 122 may be separate components. The first flow control ring 120 is annular and is installed proximate to and downstream of the fluid inlet port 50. The first flow control ring 120 extends from the housing wall outer surface 110 to the jacket wall inner surface 112. The second flow control ring 122 is also annular and is installed between the first flow control ring 120 and the fluid outlet port 52. The flow control rings 120, 122 extend from the housing wall outer surface 110 to the jacket wall inner surface 112 and are connected so that there is minimal to no fluid flow between the flow control rings 120, 122 and the surfaces 110, 112.

Fluid flow within the cooling jacket cavity 114 from the fluid inlet port 50 to the fluid outlet port 52 may take a serpentine or winding path by the provision of flow openings in the flow control rings 120, 122 as illustrated in the sequence of FIGS. 5A-5C. FIG. 5A is a cross-section perpendicular to the longitudinal axis 76 taken between the fluid inlet port 50 and the first flow control ring 120. Arrows 130 indicate fluid flow into the cooling jacket cavity 114 through the fluid inlet port 50 proximate the bottom of the cooling jacket 32. The first flow control ring 120 initially constrains the cooling fluid to flow between the mounting flange 16 and the first flow control ring 120, around the housing wall and upward toward the cutout portion 38 of the jacket wall 34. This arrangement provides the coldest cooling fluid directly to the hottest area of the motor housing 12, which is typically at the base or mount of the motor housing 12, to achieve the greatest thermal efficiency in the cooling jacket 32. As seen in FIG. 5B, which is taken between the first flow control ring 120 and the second flow control ring 122, the first flow control ring 120 has an arcuate section removed at the top to accommodate the cutout portion 38 and to provide space between ends 132 and the corresponding cutout side walls 40 to form first flow control openings 134. The first flow control openings 134 allow the cooling fluid that flowed upward from the fluid inlet port 50 between the mounting flange 16 and first flow control ring 120 to flow past the first flow control ring 120 as indicated by arrows 136 and into the area between the flow control rings 120, 122. In this area, the cooling fluid flows downward around the housing wall 14. In alternative configurations where the cutout portion 38 is omitted and the jacket wall 34 encircles the housing wall 14 in that area, the cutout portion of the first flow control ring 120 may be smaller to provide a single smaller first flow control opening 134.

FIG. 5C is taken downstream of the fluid outlet port 52 and shows the area of the cooling jacket cavity 114 between the second flow control ring 122 and the jacket end wall 36. The second flow control ring 122 has an arcuate section removed at the bottom to provide space between ends 138 to form a second flow control opening 140. The second flow control opening 140 allows the cooling fluid that flowed downward from the first flow control openings 134 between the flow control rings 120, 122 to flow past the second flow control ring as indicated by arrows 142 and into the area between the second flow control ring 122 and the jacket end wall 36. In this area, the cooling fluid flows upward around the housing wall 14 and out through the fluid outlet port 52 as indicated by arrows 144.

Introducing the cooling fluid to the lowest point or closest area to the heat source as illustrated and described herein may lower thermal equilibrium point of the motor shaft 22 and mounting components of the electric motor 10, and to lower operation setpoints. By lowering the thermal equilibrium point, the dew point condensation zone may be lower relative to the internal components of the electric motor 10 to protect the stator 70 and the bearings 46, 94. In some applications with high heat or high ambient heating zones, dew point condensation may become an issue for the moisture accumulation inside the gas-tight hermetically or vacuum sealed motor housing 12 as the cold cooling medium flows over the hot internals. The moisture may also be controlled by use of the inert gas purge port 108 of the end bell 24 as earlier described. In some conditions, compressed air or an inert gas injected at a slightly higher pressure than the internal pressure of the furnace or oven is sufficient to drive moisture pooling or build up to be forced outside the motor housing 12 or all together eliminate the potential for this phenomenon.

Alternative arrangements for controlling fluid flow through the cooling jacket cavity 114 are contemplated. For example, additional flow control rings may be added to achieve a desired flow path around the housing wall 14. Also, as an alternative to cutting out sections of the flow control rings 120, 122, the flow control rings 120, 122 may be continues circles and have flow control apertures through the flow control rings 120, 122 that are positioned during assembly to allow cooling fluid to pass flow though the flow control apertures and past the flow control rings 120, 122 at prescribed locations to achieve the desired fluid flow. Further alternative embodiments are contemplated by the inventors as having use in electric motors 10 and cooling jackets 32 in accordance with the present disclosure.

FIGS. 6-8 illustrate isometric views of a second embodiment of an electric motor 200 with fluid cooling in accordance with the present disclosure. The electric motor 200 is also a standard 3 phase A/C induction motor with many elements in common with the electric motor 10. In the drawing figures and the following discussion, similar components between the embodiments are identified by the same reference numerals. Previous discussion of the similar components for the electric motor 10 have equal application to the electric motor 200 except where noted in the following discussion. Many of the differences in the embodiments relate to the cooling mechanisms.

The electric motor 200 is ideal for similar applications as the liquid-cooled electric motor 10, but may have particular application in environments where sources for water or other cooling liquids are not available or less feasible to use. The use or requirement of water cooling often requires substantial maintenance and additional equipment for successful implementation of a closed loop cooling cycle. Additional equipment such as pumps, chillers, plumbing, flow meters, and the like are also subjected risks that are associated with high heat and water cooling. If certain parameters and application requirements cannot be met, or are difficult and costly to meet, water cooling may not be the ideal cooling strategy. For these environments, the electric motor 200 includes a cooling jacket 202 that can keep airflow concentrated tightly around the motor housing 12. The cooling jacket 202 has a jacket wall 204 surrounding and concentric with the motor housing 12. The jacket wall 204 may be substantially square in cross-section and dimensioned so that a jacket wall inner surface 206 fits tightly around the housing wall outer surface 110 of the housing wall 14 as shown in FIGS. 9 and 10. The electric motor 200 is foot mounted and includes foot brackets 208 mounted on either side of the jacket wall 204 proximate the bottom of the electric motor 200.

The jacket wall 204 is open at both ends to facilitate airflow in the longitudinal direction over the housing wall outer surface 110. The airflow is provided by an integral direct drive fan 210 mounted on the cooling jacket 202 at an end opposite the shaft end 20. The fan 210 has a fan housing 212 with a complimentary shape to the jacket wall 204 for insertion in the open end. A fan grate 214 provides a protective cover at an inlet side of the fan 210, and an aperture fan discharge wall 216 (FIG. 9) at an outlet side of the fan 210 allows airflow produced by fan blades 218 to enter a cooling jacket cavity 220 as indicated by arrows 222 in FIG. 9. A fixed frequency fan motor 224 is mounted to the fan discharge wall 216, with the fan blades 218 being mounted on a fan shaft 226 extending from the fan motor 224. The fan motor 224 may typically be synchronous to 1800 RPM or 3600 RPM to provide a constant cooling airflow at a flow rate targeted to maximize cooling efficiency. 2-pole or 4-pole fan motors 224 may be used and typically provide ample cooling velocities at these fan speeds. In some implementations, the fan motor 224 may be controlled by a VFD controller to turn down the fan speed to match ideal process conditions or flow rates. In these circumstances, or even for simply idling the fan motor 224 at a low speed to keep the furnace hot between processes or loads, the rotation of the fan blades 218 is ample to provide sufficient cooling velocities.

The fan motor 224 allows the fan 210 to be operated independent of the electric motor 200 and the rotation of the motor shaft 22. Consequently, the fan speed is adjustable to achieve a desired airflow 222 and heat transfer from the motor housing 12. The airflow 222 in the cooling jacket cavity 220 flows around the motor housing 12 in four fluid flow channels 230 (FIG. 10) defined by the jacket wall inner surface 206 at corners of the jacket wall 204 and corresponding portions of the housing wall outer surface 110 of the housing wall 14. Of course, the jacket wall 204 may have other geometries such as necessary to achieve desired airflow over the housing wall outer surface 110. Heat transfer to the exterior of the motor housing 12 is further facilitated by milling longitudinal slots or grooves 232 in the housing wall outer surface 110. The grooves 232 increase the surface area over which the air flows within the fluid flow channels 230 to draw more heat from the motor housing 12.

The electric motor 200 implements additional structures for keep heat from the high temperature environment or generated by the electric motor 200 from conducting or transferring up the motor shaft 22 to the critical components within the motor housing 12. For example, the cross-drilled heat dissipation bores 86 in the motor shaft 22 proximate the shaft end 20 and the high temperature environment remove mass from the center of the motor shaft 22. The reduced cross-sectional area of the motor shaft 22 reduces the heat transfer rate at the heat dissipation bores 86 while also providing increased exposed surface area for loss of heat to the surrounding atmosphere. Also proximate the shaft end 20, a first heat slinger 240 is mounted on the motor shaft 22 and rotates with the motor shaft 22. The first heat slinger 240 may be fabricated from a thermally conductive material such as aluminum and have a plurality of slinger fins 242. The first heat slinger 240 thermally connects the motor shaft 22 to the surrounding ambient atmosphere. As the motor shaft 22 and the first heat slinger 240 rotate, the first heat slinger 240 dissipates heat outward from the slinger fins 242. The first heat slinger 240 may also provide cooling to the fixed shaft bearing 46 as the motor shaft 22 rotates and the

In this embodiment in contrast to the electric motor 10, the motor housing 12 is not mounted to a wall of the high temperature environment in a manner that forms a gas tight or hermetic seal as can be formed with the mounting flange 16 of the electric motor 10. Instead, the fixed shaft bearing 46 may be relied upon to hermetically seal the motor housing 12. In one embodiment, the fixed shaft bearing 46 may be a rotary shaft seal of the type disclosed in U.S. Pat. No. 10,054,130 that issued on Aug. 21, 2018, and which is expressly incorporated by reference herein. Bearings such as rotary shaft seal may allow rotation of the motor shaft 22 while forming a seal to prevent unwanted contaminants from entering the motor housing 12 from the high temperature environment. The rotary shaft seal can provide isolation of the motor housing 12 from high temperature and/or chemically induced corrosive environments while allowing rotation of the motor shaft 22 extending there through. The effectiveness of the rotary shaft seal may be increased by pressurizing the seal housing bore to suppress leakage of gases through the shaft seal using a neutral inert or non-contaminating gas or lubricant. The pressurization can prevent leakage of hazardous gases from the high temperature or corrosive environment to the motor housing 12.

A second heat slinger 244 (FIG. 9) may be incorporated on the motor shaft 22 on the opposite side of the motor housing 12. The second heat slinger 244 may be mounted on the motor shaft 22 by a slinger bolt 246 threaded into a bore in the end of the motor shaft 22 in a manner that facilitates rotation of the second heat slinger 244 with the motor shaft 22. As heat is generated from the electric current flowing through the stator 70 and the rotor 74, heat is absorbed by the motor shaft 22. The integral second heat slinger 244 provides an alternate dissipation path for the heat than being transferred or conducted to the floating shaft bearing 94, the end bell 24 or other bearing support structure. As heat is conducted through the core of the material of the motor shaft 22, the cooling provided by the heat slingers 240, 244 will provide a much lower thermal equilibrium set point. The heat slingers 240, 244 on both ends of the motor shaft 22 can also act as a balancing or dynamic balancing means in the event the mass of the rotor 74 becomes unbalanced and is not easily accessible after the motor housing 12 is sealed. This may be particularly important in high RPM applications where increased amplitude levels can wear out the equipment faster. Weights may be added or removed from the heat slingers 240, 244 on either or both ends of the motor shaft 22 to balance the electric motor 200 to ISO standards prior to completing the assembly or maintenance of the electric motor 200 and installing the impeller. This balancing may be preferable, as the system may be dynamically balanced at many alternating or different frequencies more specific to resonant frequencies or magnetic imbalance at particular speeds or frequencies where the rotor 74 may rotate erratically within the motor housing 12 or the stator 70 as the motor shaft 22 deflects or the stator 70 encounters an imbalanced electrical field. The external heat slingers 240, 244 allow for balance on the far plane, where the rotor plane may be non-ideal, or the rotor 74 may already be within dynamic balance limitations at determined frequencies. As these planes are far apart and the masses from the rotor 74 or impeller may have vector imbalance points more particular to the large motor rotor 74 or large “magnet” rotor 74 that is affixed to the motor shaft 22. Balance of this plane that is very close to the heat slinger 244 may be trim balanced or dynamic balanced through the heat slinger 244 that is in very close proximity.

The illustrated embodiment also provides an alternative mechanism for connecting the shaft portions 78, 80 of the motor shaft 22. As shown in FIG. 9, the exterior shaft portion 80 has a nipple 250 that is received by a bore 252 of the motor housing shaft portion 78 to align the shaft portions 78, 80. The facing surfaces of the shaft portions 78, 80 are chamfered at the edges and welded at the seam to form a secure connection. After welding, the weld is sanded down to make a smooth, continuous surface along the motor shaft 22. The attachment mechanisms illustrated and described herein are exemplary, and those skilled in the art will understand that alternative connections are possible and contemplated by the inventor.

FIGS. 11 and 12 illustrate isometric views of a third embodiment of an electric motor 300 with fluid cooling in accordance with the present disclosure. The electric motor 300 is also a standard 3 phase A/C induction motor with many elements in common with the electric motors 10, 200. In the drawing figures and the following discussion, similar components between the embodiments are identified by the same reference numerals. Previous discussion of the similar components for the electric motors 10, 200 have equal application to the electric motor 300 except where noted in the following discussion. Many of the differences in the embodiments relate to the cooling mechanisms and to support for the motor shaft 22 and impellers (not shown) that may be mounted at the shaft end 20 of the motor shaft 22.

Similar to the electric motor 200, the electric motor 300 is ideal for similar applications as the liquid-cooled electric motor 10, but may have particular application in environments where sources for water or other cooling liquids are not available or less feasible to use. The electric motor 300 may include a fan mount assembly 302 configured for mounting and supporting the electric motor 300 when mounted on a wall (not shown) such as an external wall of a high temperature furnace through which the motor shaft 22 extends. The mounting flange 16 may be bolted or otherwise affixed to the wall and have a base plate 304 extending therefrom. Motor housing base brackets 306 extending from the bottom of the motor housing 12 are bolted or otherwise affixed to the base plate 304 to anchor the electric motor 300 to the fan mount assembly 302. A right-side lifting gusset 60R, a left-side lifting gusset 60L and base support gussets 308 (FIG. 12) rigidly connect the base plate 304 to the mounting flange 16. The lifting gussets 60R, 60L may include connection apertures 62 as discussed above, and vent slots 310 extending therethrough to allow heat to flow outward away from the first heat slinger 240 and heat fins 312 extending from the outer surface 110 of the motor housing 12. The left-side lifting gusset 60L may have a cutout section 314 along an upper edge to provide clearance for the wire terminal box 28.

In this embodiment, the cooling jacket 202 may only partially extend over the motor housing 12, and may not cover the heat fins 312. The fan housing 212 may be connected to the cooling jacket 202 and extend outward away from the motor housing 12. The contents of the fan housing 212 may be similar to that previously described, including the integral direct drive fan 210, the fan grate 214, the fan discharge wall 216 and the fan motor 224. A fan wiring box 316 may extend from the outer surface of the fan housing 212 and provide electrical connections for power and control of the fan 210. The fan 210 may be reversible to create airflow through the cooling jacket 202 and the fan housing 212 in either direction as may be necessary to dissipate heat generated during operation of the electric motor 300.

The cooling jacket 202 and the fan housing 212 may be detachably connected to each other, or permanently affixed via welds or other attachment mechanisms. In some embodiments, the cooling jacket 202 and the fan housing 212 may be integrally formed as a single unitary component. The cooling jacket 202 is configured to slide over the end portion of the motor housing 12. Cooling jacket mount flange arms 318 of a cooling jacket mount flange 320 (FIG. 13) extend radially outward at the end of the motor housing 12, and the cooling jacket 202 includes corresponding mount slots 322 that align with and receive the cooling jacket mount flange arms 318 when the cooling jacket 202 is received onto the end of the motor housing 12. Cooling jacket brackets 324 are mounted on the outer surface of the cooling jacket 202 proximate the mount slots 322 and align with the corresponding cooling jacket mount flange arms 318. Cooling jacket mount bolts 326 secure the cooling jacket brackets 324 to the cooling jacket mount flange arms 318 to secure the cooling jacket 202 and the fan housing 212 to the motor housing 12.

The cooling jacket 202 and the fan housing 212 may be further supported by a fan housing support bracket 328 that is secured to the base plate 304 of the fan mount assembly 302. A base support bracket 330 may be mounted to the bottom of the base plate 304 and align with a downward extending cooling jacket mounting flange arm 332 of the cooling jacket mount flange 320. A fan housing mount bracket 334 of the fan housing support bracket 328 may also align with the base support bracket 330 and the cooling jacket mounting flange arm 332 and be affixed thereto by fan housing mount bolts 336. While the electric motor 300 as illustrated and described herein includes the fan 210 within the fan housing 212 mounted to the cooling jacket 202, those skilled in the art will understand that the fan 210 and the fan housing 212 may be omitted from the electric motor 300 if the heat slingers 240, 244 and the heat fins 312 provide sufficient heat transfer away from the motor housing 12 in a particular implementation that the airflow generated by the fan 210 is unnecessary. In such implementations, without the fan 210 and the fan housing 212, the cooling jacket 202 may be extended if necessary to fully enclose the second heat slinger 244, and the fan grate 214 may be attached to the end of the cooling jacket 202 to reduce the risk of operators coming into contact with the second heat slinger 244 when it is spinning at high velocities.

FIGS. 13 and 14 illustrate isometric and side views, respectively, of the electric motor 300 with the cooling jacket 202, the fan housing 212 and the right-side lifting gusset 60R removed to better illustrate the motor housing 12, the second heat slinger 244 and an external bearing 340 mounted to the base plate 304 and supporting the motor shaft 22. The external bearing 340 may be a pillow block-type bearing mounted on the base plate 304 with an intervening bearing shim 342 that is sized to raise the external bearing 340 above the base plate 304 so that the motor shaft 22 is aligned with the longitudinal axis 76 of the electric motor 300. Providing the external bearing 340 separate from the motor housing 12 may simplify the design of the motor housing 12 and the components therein, and may eliminate the need for having a shaft bearing mounted to or within the motor housing 12 between the rotor 74 (FIG. 15) and the external bearing 340. The high operating speeds of the electric motor 300 and the weight loading and centrifugal forces generated by the overhung impeller mounted at the shaft end 20 of the motor shaft 22 increase the size of the bearings required to support the motor shaft 22. The electric motor 300 in accordance with the present disclosure reduces the cost and engineering involved with integrating larger bearings into the design of the motor housing 12. Replacement of the motor housing bearings with the external bearing 340 simplifies the design of the electric motor 300 while facilitating implementation of bearings having the capacity required to bear the loading on the motor shaft 22.

FIGS. 13 and 14 also more clearly illustrate the motor housing 12 being formed from separate components to facilitate assembly of the components within the motor housing 12. The motor housing 12 may include a main housing portion 350 that is generally cylindrical and from which the heat fins 312 extend radially outward. A first housing end cover 352 is mounted to a first end of the main housing portion 350 and a second housing end cover 354 is mounted to a second or opposite end of the main housing portion 350. As shown in the cross-sectional view of FIG. 15, the housing portions 350-354 combine to define the housing wall inner surface 72 and the housing wall outer surface 110. The housing portions 350-354 may be attached during assembly to form the motor housing 12 via bolts or other appropriate attachment mechanisms that may secure the housing portions 350-354 together while allowing for disassembly if necessary to perform maintenance on the electric motor 300.

The shaft end 20 of the motor shaft 22 extends outward through a first shaft opening 356 of the first housing end cover 352. A lip seal 358 similar to the lip seal 104 may be installed at the first shaft opening 356 to prevent debris from entering the motor housing 12 through the first shaft opening 356. The motor shaft 22 may have a similar configuration as discussed above with the motor housing shaft portion 78 being fabricated from a conductive material and the exterior shaft portion 80 being fabricated from a non-conductive, high temperature resistant material. In this embodiment, the motor housing shaft portion 78 extends from the first housing end cover 352 and is received by the external bearing 340. To accommodate this arrangement, the splined bore 84 of the shaft connect may be formed in the motor housing shaft portion 78 and the splined male end 82 may be formed at the corresponding end of the exterior shaft portion 80. The first heat slinger 240 may be mounted to the exterior shaft portion 80 proximate the motor housing shaft portion 78 and the external bearing 340, with the heat dissipation bores 86 being formed in the exterior shaft portion 80 outward from the first heat slinger 240.

The electrical components of the electric motor 300 are installed within the main housing portion 350. The stator 70 is mounted to the portion of the housing wall inner surface 72 within the main housing portion 350, and is held stationary relative to the housing wall 14. The rotor 74 is mounted on the portion of the motor housing shaft portion 78 disposed within the main housing portion 350 and rotates with the motor shaft 22 about the shaft longitudinal axis 76. The external bearing 340 and the bearing shim 342 are sized to align the rotor 74 within the stator 70 with a gap therebetween to allow for rotation without contact between the stator 70 and the rotor 74.

A portion of the motor housing shaft portion 78 opposite the splined bore 84 may extend through a second shaft opening 360 of the second housing end cover 354. The end bell 24 substantially as described above may be attached at an outward end of the second housing end cover 354 so that the end of the motor housing shaft portion 78 may extend through lip seal 104 and the floating shaft bearing 94. The cooling jacket mount flange 320 may be mounted to the end bell 24 and/or the second housing end cover 354 with the cooling jacket mount flange arms 318, 332 aligned for attachment of the cooling jacket 202 and the fan housing 212.

FIG. 16 illustrates an alternate embodiment of the electric motor 300 with the second heat slinger 244 replaced by an axial impeller 370 on the end of the motor housing shaft portion 78 of the motor shaft 22 to create more airflow over the motor housing 12. In some embodiments, the axial impeller 370 may be of the type illustrated and described in U.S. Pat. No. 10,605,262 that was issued to Johansen on Mar. 32, 2020, and which is expressly incorporated by reference herein. The pitch of the blades of the axial impeller 370 may dictated by the direction of rotation of the electric motor 10 so that air flows over the motor housing 12 in the desired direction.

FIG. 16 further illustrates the incorporation of a guard 372 covering the first heat slinger 240 and the external bearing 340. When installed, the guard 372 limits access by operators and maintenance personal when the electric motor 300 is operating to prevent injury. A similar guard 372 may be provided on the electric motor 200 to cover the first heat slinger 240 in that embodiment. The guard 372 may be configured to facilitate removal when necessary to access the first heat slinger 240, the external bearing 340 or other components of the electric motors 200, 300 enclosed thereby.

While not illustrated herein, the electric motors 10, 200, 300 may allow for mounting and use of conventional thermocouples at various locations, such as on surfaces of inboard bearings, the motor housing 12 and the like. The thermocouples may be operatively connected to a control device for the environment or process for which the electric motors 10, 200, 300 provide airflow. An operator may be able to monitor the information from the thermocouples and make appropriate adjustments to the operation of the electric motor 10, 200, 300 in response. The information may also allow a control program to adjust the motor speeds necessary to produce a desired airflow as long and the information from the thermocouples indicates that the electric motor 10, 200, 300 is not at risk of damage due to overheating.

INDUSTRIAL APPLICABILITY

The various electric motor designs in accordance with the present disclosure can improve cooling of the components of the electric motor and the overall performance of the electric motors. Electric motors in accordance with the present disclosure may have use in implementations where hermetic, vacuum or gas tight sealing arrangements are required, but still require a rotating medium such as a fan impeller. The electric motors may be used in vacuum heat treating vessels or in environments containing toxic or explosive gases such as hydrogen that is explosive if exposed to oxygen, or outside ambient atmosphere or ammonia that is corrosive to copper. The direct drive assembly of the electric motors, when coupled with the appropriate fan blade or impeller, can act as a cooling fan or a recirculating fan for these vessels and environments where standard fan or rotary sealing arrangements will not suffice.

Also, typically air cooled models are ideal where belt driving the impeller becomes a maintenance issue or controlling the motor through a VFD controller is required or ideal to control the fan or impeller performance on the fan shaft. Some processes require multiple or a plethora or fan RPMs to control performance of the fan while the product or process is being maintained, such as glass tempering, or when providing an air or cooling quench to the processed parts is needed for only a period of time and not continuous. This can be done using the direct drive motor where utilizing standard method of belts and pulley and operating at low or high turndown on the motor will not provide sufficient motor cooling rates to the totally-enclosed, fan cooled (TEFC) frame motor being used, as this type of cooling method on this motor, the cooling fan located within the TEFC motor operates at the same synchronous speed as the motor turning, which is not ideal for low RPM or large turndown.

The air cooled models may also be advantageous where belt driving the impeller at high ambient temperatures creates maintenance issues due to a need for frequent tensioning adjustment for the belt, degradation of the belt reducing its lifespan, or other adverse operating conditions. Eliminating belt drives also improves the compactness of the arrangement by eliminating motor pedestals, drive belts, pulleys, bushings, personnel safety guarding and other belt-specific components that would require a much larger area or footprint for the drive arrangement than may be available in many implementations.

While the preceding text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the scope of protection.

It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. 

What is claimed is:
 1. An electric motor comprising: a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface, a housing wall outer surface, a first motor housing end and a second motor housing end; a stator mounted to the housing wall inner surface; a motor shaft mounted for rotation within the housing wall and having a first shaft end extending out of the first motor housing end, a second shaft end extending out of the second motor housing end and a shaft longitudinal axis; a rotor mounted on the motor shaft and aligned with the stator; a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity; a first heat slinger mounted on the first shaft end; and a second heat slinger mounted on the second shaft end and disposed within the cooling jacket.
 2. The electric motor of claim 1, comprising a fan mounted to the cooling jacket with the second heat slinger dispose between the motor housing and the fan, the fan being operable to generate airflow parallel to the shaft longitudinal axis.
 3. The electric motor of claim 2, wherein the fan comprises a direct drive fan that is controllable to rotate independent of the rotation of the motor shaft and the second heat slinger.
 4. The electric motor of claim 2, wherein the cooling jacket extends longitudinally toward the first motor housing end and is disposed radially outward from the stator and the rotor such that the airflow generated by the fan flows over the portion of the motor housing surrounding the stator and the rotor.
 5. The electric motor of claim 1, wherein the motor housing is mounted on a base plate of a fan mount assembly, and wherein the electric motor comprises an external bearing mounted on the base plate and receiving and supporting the first shaft end.
 6. The electric motor of claim 5, wherein the external bearing is disposed between the motor housing and the first heat slinger.
 7. The electric motor of claim 1, comprising a floating shaft bearing mounted to the second motor housing end and receiving and supporting the second shaft end, wherein the floating shaft bearing is moveable parallel to the shaft longitudinal axis in response to expansion and contraction of the motor shaft.
 8. An electric motor comprising: a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface and a housing wall outer surface; a stator mounted to the housing wall inner surface; a motor shaft mounted for rotation within the housing wall and having a shaft longitudinal axis; a rotor mounted on the motor shaft and aligned with the stator; a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity; and a cooling fan mounted at an open end of the jacket wall and upstream from the housing wall to discharge air into the cooling jacket cavity, wherein the air discharged from the cooling fan flows longitudinally through the cooling jacket cavity and along the housing wall outer surface.
 9. The electric motor of claim 8, wherein the jacket wall has a square cross-section, and wherein the jacket wall inner surface at each corner of the jacket wall and a corresponding portion of the housing wall outer surface define a fluid flow channel for airflow from one end of the jacket wall to an opposite end of the jacket wall.
 10. The electric motor of claim 9, wherein the air discharged from the cooling fan flows longitudinally along the housing wall outer surface through the fluid flow channel.
 11. The electric motor of claim 8, wherein the housing wall has a plurality of grooves extending longitudinally in the housing wall outer surface and being circumferentially spaced about the housing wall outer surface.
 12. The electric motor of claim 8, wherein the motor shaft comprises: a motor housing shaft portion disposed within the housing wall with the rotor mounted thereon, wherein the motor housing shaft portion is fabricated from an electrically conductive material; and an exterior shaft portion connected to the motor housing shaft portion and disposed outward of a first motor housing end of the housing wall, wherein the exterior shaft portion is fabricated from material having a melting point greater than 2200° F.
 13. The electric motor of claim 8, wherein a first shaft end of the motor shaft extends out of a first motor housing end of the motor housing and a second shaft end of the motor shaft extends out of a second motor housing end of the motor housing, and wherein the electric motor comprises: a first heat slinger mounted on the first shaft end; and a second heat slinger mounted on the second shaft end and disposed within the cooling jacket cavity.
 14. The electric motor of claim 13, wherein the motor housing is mounted on a base plate of a fan mount assembly, and wherein the electric motor comprises an external bearing mounted on the base plate and receiving and supporting the first shaft end.
 15. An electric motor mounted on a base plate of a fan mount assembly, the electric motor comprising: a motor housing having a housing wall having a cylindrical shape, a housing wall inner surface, a housing wall outer surface and a motor housing base bracket extending from the housing wall outer surface and affixed to the base plate; a stator mounted to the housing wall inner surface; a motor shaft mounted for rotation within the housing wall and having a shaft longitudinal axis and a first shaft end extending from a first motor housing end of the motor housing; a rotor mounted on the motor shaft and aligned with the stator; a cooling jacket having a jacket wall surrounding and concentric with at least a portion of the housing wall and having a jacket wall inner surface and a jacket wall outer surface, wherein the housing wall outer surface and the jacket wall inner surface define a cooling jacket cavity; and an external bearing external to the first motor housing end and mounted on the base plate, wherein the external bearing receives and supports the first shaft end.
 16. The electric motor of claim 15, wherein no additional shaft bearing is disposed between the external bearing and the rotor.
 17. The electric motor of claim 15, comprising a first heat slinger mounted on the first shaft end with the external bearing disposed between the first motor housing end and the first heat slinger.
 18. The electric motor of claim 15, wherein the motor housing has a second motor housing end opposite the first motor housing end and the motor shaft has a second shaft end extending from the second motor housing end, the electric motor comprising a floating shaft bearing mounted to the second motor housing end of the motor housing and receiving and supporting the second shaft end, wherein the floating shaft bearing is moveable parallel to the shaft longitudinal axis in response to expansion and contraction of the motor shaft.
 19. The electric motor of claim 18, comprising: a first heat slinger mounted on the first shaft end with the external bearing disposed between the first motor housing end and the first heat slinger; and a second heat slinger mounted on the second shaft end external to the second motor housing end.
 20. The electric motor of claim 19, wherein the jacket wall extends away from the second motor housing end to fully enclose the second heat slinger. 